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A024156
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Number of integer-sided triangles with sides a,b,c, a<b<c, a+b+c=n that are obtuse.
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6
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0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 1, 2, 2, 3, 2, 4, 3, 6, 3, 7, 4, 8, 6, 9, 7, 10, 8, 12, 10, 15, 11, 16, 13, 18, 15, 19, 17, 21, 19, 25, 21, 28, 22, 30, 25, 32, 28, 35, 31, 38, 33, 41, 35, 45, 38, 47, 42, 51, 46, 53, 50, 57, 52, 61, 55, 65, 58, 68, 63, 74, 67, 77, 71, 82, 74, 86, 77, 92, 82, 96, 87
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OFFSET
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1,13
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LINKS
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Jean-François Alcover, Table of n, a(n) for n = 1..200
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MATHEMATICA
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r[n_] := Module[{a, b}, Reduce[a>1 && a<b && a + 2b < n && 2(a + b) > n && 2n(a + b) < 2a*b + n^2, {a, b}, Integers]];
a[n_] := Module[{rn = r[n]}, Which[rn === False, 0, rn[[0]] === And, 1, rn[[0]] === Or, Length[rn], True, Print["error: ", n, " ", rn]]];
Array[a, 84] (* Jean-François Alcover, Mar 01 2019 *)
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CROSSREFS
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Cf. A024154, A024155.
Sequence in context: A127682 A127685 A127687 * A241316 A241312 A075989
Adjacent sequences: A024153 A024154 A024155 * A024157 A024158 A024159
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling
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STATUS
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approved
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